1. Field of the Invention
The present invention relates to a valve device suitable for use with a gas tank or the like for storing high-pressure gas and also relates to a manually operated shutoff valve device using the valve device.
2. Discussion of the Related Art
Generally, a plug body for closing an opening portion of a gas tank is provided therein with a plurality of flow passages which make the interior and exterior of the gas tank communicate, and a plurality of valve devices such as, for example, manually operated shutoff valves for blocking the flow of high-pressure gas in the respective flow passages. As a valve device of this kind, there has been known one which is described in EP 1 813 856 A1 (equivalent of JP 2006-144841 A1).
The valve device (manual valve) described in the European patent application is provided with a housing (35) taking a bottomed, cylindrical shape, a valve body (36) held in the housing slidably in the axial direction thereof and an operating screw (37) for operating the valve body. At an bottom portion of the housing, there is formed a through hole (38) communicating with a through hole (32) of a check valve (9), and a valve seat (40) of a taper shape which the valve body (36) seats on and goes away from is formed at the circumferential edge of the through hole (38). On one hand, a taper surface is formed at an extreme end portion (36a) of the valve body (36) and seats on the valve seat (40) to close the through hole (38), so that the flow of hydrogen gas in a filling passage can be blocked.
By the way, in recent years, the pressurization in hydrogen gas tanks equipped on fuel cell vehicles or the like has been accelerated for increase in storage capacity, wherein higher reliability which meets the accelerated pressurization has been required. To this end, the aforementioned housing (35) and the valve body (36) have been made of a metal such as stainless steel.
However, since the prior art described in the European patent application is constructed to close the through hole by bringing the valve body into taper surface contact with the valve seat formed on the housing, there arises a problem that precise machining is required for high coaxial alignment between the valve body and the valve seat in securing precise airtightness.
In order to meet the requirement, it may be conceived to make the housing forming the valve seat with a soft metal material such as, for example, aluminum or the like. In this case, there is taken a construction that the housing and the valve body are respectively made of aluminum and stainless steel. Where the construction is taken to use different metal materials, however, there is a risk that abnormal deformation takes place at the sealing portion due to the line-contact or deformation which occurs when the valve is closed. This leads to another risk that burs made by the deformation separate and flow as foreign matter throughout the system, deteriorating the function of the valve device.